The most extensively used method currently employed to dye keratin fibers, such as hair, is by an oxidative process that utilizes one or more oxidative dye compounds in combination with one or more oxidizing agents.
Commonly, a peroxy oxidizing agent is used in combination with one or more developers or couplers, which are generally small molecules capable of diffusing into hair. A wide variety of oxidants may be used to generate the reactive developer species. Generally, a peroxide material, such as hydrogen peroxide, activates the developers so that they react with the couplers to form larger sized compounds in the hair shaft to give a variety of shades and colors.
A wide variety of developers and couplers have been employed in such oxidative hair coloring systems and compositions. However, there still exists a need for additional keratin dyeing compounds which can act as developers and/or couplers and which can safely provide color benefits.
Hydrogen peroxide-mediated transformation of arylboronic acids or arylboronic esters to phenols has been investigated to develop highly selective and sensitive probes for hydrogen peroxide, which is one of the major reactive oxygen species (“ROS”) in living cells. The kinetics of the reaction between hydrogen peroxide and phenylboronic acid was investigated by Henry G. Kuivila et al., J. Am. Chem. Soc. 1957, 79, 5659, who proposed the following mechanism:

Additionally, the transformation of boronic acids and boronic esters to the corresponding alcohols by the use of Oxone™ in aqueous acetone buffered with sodium bicarbonate has been described by Kevin S. Webb et al., Tetrahedron Letters, 1995, 36, 5117.
More recently, the syntheses and biological applications of fluorescent probes for hydrogen peroxide have been reported by Michelle C. Y. Chang et al., J. Am. Chem. Soc., 2004, 126, 15392 and 2005, 127, 16652. These peroxysensors utilize a boronate-hydrogen peroxide reaction to provide high selectivity for detecting hydrogen peroxide in aqueous solution. The boronate compound is non-fluorescent and displays no absorption in the visible region. The addition of hydrogen peroxide triggers immediate increase in fluorescence and growth of visible wavelength absorption bands characteristic fluorescein and red-fluorescent resorufin, as shown in the following mechanisms, respectively:

The aforementioned references, however, do not disclose the use of such boronic acid and boronic ester compounds in compositions for oxidatively dyeing keratin fibers.
It has now been discovered that certain aromatic systems comprising at least one boronic acid or boronic ester moiety are capable of imparting commercially desirable colors to keratin fibers, such as hair. Such boronic acid or boronic ester compounds are capable of providing dyeing results comparable, in terms of color and intensity, to those achieved by using known oxidative dye compounds. Accordingly, there exists a need for keratin fiber dyeing compositions which comprise aromatic systems comprising at least one boronic acid or boronic ester moiety.